The double logic of leaving the most powerful centre-right force in the European Parliament was that the Conservatives should not be in a group that supports “ever-closer union”, but should instead be in a group that opposes it. It follows from helping to form that latter alliance, the European Conservatives and Reformists Group, that it should be as large and strong as possible – and keep growing.

It therefore also follows that it will strengthened by the new presence of the Alternative für Deutschland party. The ECR announced earlier this morning that the AfD has joined it. As Andrew Gimson and I have pointed out, the latter is a mainstream, Eurosceptic party – “painfully respectable”, as Andrew put it. For what it is worth, we too welcome the ECR’s new partner.

David Cameron will not share this view, and his reasons are far from contemptible. It is true that Angela Merkel will be angered by this move; that it may end his plans to block Jean-Claude Juncker, and that Merkel’s anger may last longer, and have more damaging consequences, than her anger over Tory MEPs leaving the EPP and forming the ECR group in the first place.

She may thus be less inclined to be helpful than before in relation to Cameron’s renegotiation plans. But these are in any event fairly modest. If you doubt it, let Mark Wallace be your guide to the Prime Minister’s very limited plans to control EU immigration. Today’s AfD decision is a stark reminder of the gap that separates the Christian Democrat and Conservative visions of Europe.